Abstract:
A micro air vehicle (MAV) is a semiautonomous airborne vehicle which measures less
than 15 cm in any dimension. It can be used to access situations too dangerous for direct
human intervention, e.g., explosive devices planted in buildings and video
reconnaissance and surveillance, etc. As demonstrated by flying birds and insects,
flapping flight is advantageous for its superior manoeuvrability and much more
aerodynamically efficient at small size than the conventional steady-state aerodynamics.
Piezoelectric actuators are easy to control, have high power density and can produce
high output force but usually the displacement is small. With appropriate stroke
amplification mechanisms piezoelectric actuators can be used to drive the flapping
wings of MAV.
This research aims to develop a piezoelectric fan system with 2 degrees of freedom of
motion for flapping wing MAV applications. In this project, piezoelectric fans
consisting of a piezoelectric layer and an elastic metal layer were prepared by epoxy
bonding. A flexible wing formed by carbon fibre reinforced plastic wing spars and
polymer skin was attached to two separate piezoelectric fans to make them coupled.
Two sinusoidal voltages signals of different phase were then used to drive the coupled
piezoelectric fans. High speed camera photography was used to characterize the two
degrees of freedom motion of the wing. Theoretical equations were derived to analyse
the performance of the piezoelectric fans in both quasi-static and dynamic operations,
and the calculated results agreed well with the finite element analysis (FEA) modelling
results. It has been observed that the phase delay between the driving voltages applied
to the coupled piezoelectric fans plays an important role in the control of the flapping v
and twisting motions of the wing. Selected factors such as the gap between the two
piezoelectric fans which can affect the performances of the wing have been investigated
and the experimental results were compared with the FEA modelling results.
